1. Field of Invention
The present invention relates in general to test and measurement equipment, and more specifically to an apparatus and method for measuring, recording, analyzing and reporting the operating velocity, deceleration, jerk, that is rate of change of change, and stopping distance of the steps, treadboards, pallets, treadway, or conveyor mechanism and the moving handrails of an escalator, moving walk, or other conveyor mechanism and in particular to such an apparatus which may form a portable measurement tool.
2. General Background
Escalators and moving walks are equipped with electro-mechanical braking systems that bring the steps and handrails of the escalator to a rapid stop whenever any one of the numerous safety devices in the escalator is activated. Excessively rapid deceleration causes riders to be thrown forward, possibly resulting in injury. Slow or delayed deceleration results in prolonged stopping distances which can compound injuries and damage resulting from entrapments between the moving and stationary elements of the escalator, including the comb sections located at each landing. US Consumer Product Safety Commission statistics indicate that there are thousands of reported escalator and moving walk injuries annually. The severity of injury and damage resulting from virtually all escalator accidents are affected by the rate of deceleration and the stopping distance of the escalator. In most jurisdictions, the maximum deceleration rate and the maximum stopping distance are regulated by a legally mandated Safety Code. Most jurisdictions employ or contract with inspectors to ensure Safety Code compliance.
One way of measuring step velocity is by manually applying a hand held tachometer to the handrails and manually recording its velocity. Then riding the escalator or moving walk and applying a tachometer to the balustrade to ascertain step velocity, and manually recording the results. These techniques are imprecise, prone to recording errors, difficult to duplicate precisely, and do not provide data related to stopping distances or deceleration.
Another known procedure is that of initiating a braking action by manually tripping a safety device, e.g., emergency stop switch, when a particular step, treadboard, or pallet or point on a treadway or conveyor mechanism passes a predetermined point, e.g., a mark on the skirt panel of the escalator, a skirt safety switch or a missing step detector, and then manually measuring the distance traveled using a rule or tape measure. These techniques are also imprecise, prone to recording errors, difficult to duplicate precisely, and do not actually evaluate the action of the braking system, i.e. discern differences between coasting and active brake retardation. Nor do they provide sufficient data to calculate the actual rate of deceleration or jerk. The inability to evaluate the action of the braking system means that such techniques fail to address the actual Safety Code limitations on maximum deceleration rate which is expressed as a formula, e.g, 3 ft/sec.sup.2 or 0.9 m/s.sup.2
Deceleration can also be measured and recorded by using ad hoc test rigs consisting of a rotary encoder device which is applied to the motor shaft or drive shaft of an escalator or moving walk and a circuit monitor connected to the safety circuit. Test data is recorded either with a paper chart recorder or using a personal computer. These techniques correlate the initiation of braking action with velocity data, and support deceleration analysis. However, they are invasive and time consuming to set up, often taking hours to complete. They require that the escalator be barricaded against public access, that power be removed from the escalator, that access panels, landing plates and sometimes steps be removed, that encoders be mounted on the motor or drive shaft, and that circuit probes be connected to the safety or brake circuit.
Then too, velocity and deceleration measurements may be obtained using accelerometers placed on a moving step or handrail. This technique supports deceleration analysis. However, because it fails to account for the initiating event of the braking action, the analysis cannot detect delays in the activation of the brake mechanism. Such delays can exacerbate injuries, and may constitute a violation of Safety Code requirements.
It would therefore be desirable to have measurement equipment for measuring velocity, deceleration, jerk and stopping distances of escalator steps, treadboards, pallets, treadway or conveyor mechanism and the moving handrails of an escalator, moving walk or other conveyor mechanism, which is free of the deficiencies noted above.